EmbeddingGemma 2: an open, lightweight multimodal embedding model
deepmind.google·6d ago
AI Engineering
Hacker News·Aug 17·5 min read
How do functions like alloca allocate memory from the stack?
TL;DR
The _alloca function allocates memory on the stack by probing the stack space before adjusting the stack pointer. This ensures that large allocations do not bypass the guard page, preventing stack overflows.
✦ Why It Matters
Consider using _alloca for stack-based memory allocation to improve performance in your applications.
Key Takeaways
- Use _alloca() for dynamic stack memory allocation.
- Always ensure stack probing with _chkstk() for large allocations.
- Understand the implications of stack overflows in your code.
- Familiarize yourself with x86-64 assembly for better memory management.
How It Works
The _alloca() function allocates memory on the stack by first calling _chkstk() to probe the stack. This probing checks if there is enough space available, preventing overflows.
The process involves adjusting the stack pointer only after confirming sufficient space, ensuring safe memory allocation.